1. Field of the Invention
The present invention relates to a glass and a glass ceramic composition, which are suitable for forming a dielectric by low temperature firing, a dielectric suitable for e.g. a substrate for e.g. an antenna or circuit to be used in a high frequency region, and a process for producing a laminated dielectric suitable for such a substrate.
2. Discussion of Background
A dielectric is employed for a substrate for e.g. a resonant filter or an antenna to be used in a high frequency region, and such a dielectric is required to have a high dielectric constant. Many glasses have been proposed as such dielectric materials (e.g. Tables 1 and 2 in JP-A-7-118060).
Such a dielectric having a high dielectric constant may, for example, be laminated with a dielectric having a low dielectric constant for use as a circuit board (e.g. JP-A-2001-284807).
In recent years, such a dielectric material is required to be capable of being fired at a low temperature (for example, capable of being fired at a temperature of at most 900° C.), to contain no lead and further to have a low content of alkali metal oxides in order to improve electrical insulation properties.
It is an object of the present invention to provide a non-lead glass for forming a dielectric, a glass ceramic composition for forming a dielectric, and a dielectric, which are capable of satisfying such requirements.
Further, in a case where a layer having a high dielectric constant and a layer having a low dielectric constant are to be laminated, it is conceivable, as disclosed in JP-A-2001-284807, to adopt a method of laminating and unifying layers having mutually different compositions, followed by firing. However, layers having different compositions may usually take different firing shrinkage behaviors in many cases, and have had a problem such that interlaminar peeling, deformation or the like is likely to result.
It is another object of the present invention to provide a process for producing a laminated dielectric which is capable of solving such a problem.